Blowpipe



March 18, 1941.

R. J. KEHL BLowrIPx-z Filed May 5, 1939 lNvEN'roR ROBERT J. KEHLATTORNEY Patented Mar. 18, 1941 BLOWIIPE ,Robert J. Kehl, Manhasset, -N.Y., assignor to Oxweld Acetylene Company, a corporation of West VirginiaApplication May 3,1939, serial No. 271,447 9 claims. (c1. 15s-27.4)

This invention relates to blowpipes such as those used for welding andcutting metals, and more particularly to means for eliminating backfringwithin the blowpipe when the gas supply is shut oi,

Blowpipes frequently are provided with tw pairs of valves, the main pairbeing used to carefully adjust the mixture of oxygen and acetylene tothe desired proportions, and an auxiliary pair of valves being employedto quickly turn on and shut off the flow of gas without disturbing themixture proportions. Accordingly, the main or mixture-controlling valveswhen oncev adjusted may be left untouched during an 4entire working day,while the now of gas mixture may be controlled by operation of theauxiliary or gas-saver valves which are quickly and convenientlyoperated at the beginning and end `of each heating operation. A blowpipehaving suchv main mixture valves and auxiliary or gas-saver valves isdisclosed in my Patentl 2,191,078, dated February 20, 1940.

It has been found that 'when the gas-saver valves are operatedsimultaneously to shut off the flow of combustible mixture to the tip,popping or backring may result as soon as the forward velocity of thegases kfalls below the backward ame propagation rate, producing a smallexplosion that depositsl soot within the blowpipe stem, and which isotherwise annoying to the operator. The Vexplosion hazard may besubstantially eliminated by rapidly` expelling the residual gas mixtureimmediately after the supply o-f gas is shut off. Asv described inthesaid Patent No. 2,191,078, this result maybe eiected by causing thegas-saver valves to operate in sequence, for example, by so releasingthe gas-saver valve lever, that it closes'oif'the supply "of acetyleneat a moment beforeV shutting off 'the oxygen. The momentary continuedflow of oxygen is effective to maintain theexit velocity of the mixtureat the tip suiiciently high to prevent backward flame propagation, whilediluting the combustible mixture so that at the time the velocity ofgases within the blowpipe diminishes to below the backward amepropagation rate, no tendency for popping exists.

Frequently the respective gas-saver valves are operated in such rapidsuccession that insuflicient time remains for one gas to evacuate theother, and a tendency towardv backringpersists. Devices, such asdash-pots, and the like, have been proposed to delay the operation ofone valve and thus insure substantially complete evacuation of theresidualmixture by one of the gases.

Such devices are relatively velaborate and expensive and may requiremaintenance and repair.

According to the present invention, simplified means is provided forevacuating the residual 5 mixture immediately upon closing of thegassaver valves. The simplified means produces an eifect similar to thatobtained by retarding the operation of the second valve. By properdesign,

the improved means'may be employed to evacu-v 10y ate the vresidual gasmixture even though the' gas-saver valves are operated simultaneouslyrather than in sequence. The invention requires no moving'parts and nocomplicated structure such as would require adjustment or repair.

Accordingly, the principal objects of the present invention are: toprovide an improved blowpipe having quick-acting gas-saver valves andimproved means for eliminating the tendency for the gases to backre whenthe gas-saver valves 20 are closed; to provide, in a blowpipe havingsequentially operated gas-saver valves, means for assisting theevacuation of the residual gas mixture when the valves are shut off; andto provide means having no moving parts, adapted to 25 p operate inconjunction with quick-acting gassaver valves to assist in evacuatingthe residual gas mixture. These and other objects and the novel featureswill appear from the present speciiicatio'nY and the yaccompanyingdrawing, dis- 30 closing one embodiment of the present invention, In thedrawing- Fig. 1 is a side elevational View of a welding blowpipe withportions of the handle broken away to disclose the `internal structure;35

' Fig. 2 is a longitudinal sectional view taken on the ,line 2-2 of Fig.1;v

Fig. 3 is a cross-sectional view taken on the line13-3 of Fig, 1; and

,Fig 4 isa longitudinal sectional View of a 40 flow from a rear valvevblock V to a blowpipe 50,

stem S at the forward end of the blowpipe. The flow of fue-l gas andcombustion-supporting gas, hereinafter referred to as acetylene andoxygen respectively, is controlled by a pair of quick-acting gas-savervalves'G. Thelvalves G are locat- 55 ed in the gas conduits throughwhich the gases flow and are constructed so as to close automaticallyand may be opened manually by depressing a lever. A reservoir R islocated in one of the conduits, preferably in the oxygen conduit, at apoint between the gas-saver valves and a mixer M to serve as a uidcushion for assisting in the discharge of residual gases when the gassupply is suddenly shut oif by the gas-saver valves G.

The blowpipe B is provided with inlet nipples I0 and I I for connectionwith sources of acetylene and oxygen respectively. The gases enter thevalve block V where the correct proportions' of the respective gases areinitially adjusted, as by means of a pair of main mixture-controllingvalves I4 and I5. The ow of gas may be additionally controlled, that is,completely turned on or shut off, by a pair of auxiliary valves Gcomprising manually openable and automatically closing acetylene andoxygen valves I 2v and I3, respectively. The valves G are normallyresiliently held in closed position but may be opened either`concurrently or in sequential order by a pair of manually depressiblelevers I6 and I`I which engage the stems of the respective valves andextend forwardly adjacent to the handle H for convenient manipulation bythe operator. Further details of construction of the valves G and theiroperating levers are fully disclosed in my Patent 2,191,078, da-tedFebruary 20, 1940. An acetylene conduit I'8 and an oxygen conduit 2i]deliver the respective gases from the discharge end of the valves Gtothe mixer M from whence the gas mixture may pass through the stem S to aburner tip T. The stem S is secured to the handle H by means `of aconventional coupling nut I9.

An unventilated reservoir or large-capacity chamber R communicates with`the oxygen passage at a point between the discharge port of the oxygenvalve I3 and the mixer M. As shown in Fig. 2, the reservoir R maycomprise a branch tube 22 sealed at one end 23, `as by flattening andsoldering. TheI opposite end of the branch tube 22 connects with aninlet passage 24 which com- R may `comprise a suitable enlarged zone 25of' the oxygen conduit 2U, as shown in. Fig. 4. Otherwise, ifa chamber26 (Fig. 2) may be formed and hermetically sealed within the handle H,it may serve as an enlarged reservoir in place of the tube 22,connection being made with the oxygen conduit 2|' through the inletpassage 24.

The functioning of the improved means Will become obvious from .thefollowing description of the operation of the blowpipe. With the inletnipples I0 and II suitably connected to the respective sources of gassupply, the levers I6 and I'I are manipulated so as to open the valvesG, and the mixture-control valves I4 and I5 are adjusted to deliver theydesired mixture, as evidenced by the appearance of the ame issuing fromthe tip T. At the completion of a heating operation, the operatorreleases the levers I6 and I'I so as to shut off the supply of gasesabruptly without disturbing the mixture adjustment. Even though therespective gas-saver valves I2 and I3 operate successively, the delayed`operation of,

for example, the oxygen valve I3, may not be suflicient to completelyevacuate the residual combustible mixture from the stern Si by the timethe supply of oxygen is shut 01T. The reservoir R contains apredetermined quantity of oxygen at substantially operating pressure,for example, from 15 to 30 pounds per square inch, which oxygencommunicates with the atmosphere only through the tipvT. ,As soon as thesupply of gas to the reservoir is shut 01T by the operation of thegas-saver valve, the compres-sed gas within the oxygen reservoir,including the Iconduit 20, flows toward the outlet in the tip T, whichoutlet forms the only exit passage from the unventilated chamber orreservoir R and the gas conduits. The flow initially progresses at highspeed because of the relatively high pressure within the reservoir, andthe quantity of released gas is suicient to evacuate substantially allof the residual combustible mixture located between the mixer and Ithetip` T at a high exit velocity. If the valves G are operated insequence, the exhausting of the combustible mixture by the gas releasedfro-rn the reservoir R, is assisted by the continued momentary i'lowfrom the oxygen conduit. Thus, the gas from the reservoir is capable ofacting alone to exhaust lthe residual gases, that is, when bothgas-saver valves are operated concurrently, `or the gas from thereservoir may assist in the evacuation produced by a retarded operationlof the oxygen valve, in which event the Itrapped gas in the reservoirprovides a continued iiow of oxygen over a longer period than isordinarily obtained by sequentialv operation of the valve-s I2 and- I3.

Although a separate reservoir R has been shown in Fig. 2, the reservoirincludes, in effect, the volume of the oxygen conduit' between thevalves G and the mixer M, which conduit or reservoir communicates Withthe atmosphere-only through the tip T. Similar results are obtainable byan enlargement of the conduit 20 as shown in Fig. 4. Ordinarily, thevolume of the oxygen conduit is less lthan that of the acetylene`conduit because of the larger tubing required to provide the necessaryflow of acetylene at the usual low operating pressures. In the presentcase, however, the total volume of the combined oxygen conduit 2D andthe reservoir R is substantially equal to the volume of the acetyleneconduit. Under typical operating conditions, as when the oxygen pressureis 30 pounds per square inch, and the acetylene pressure is a two poundva-cuum, the oxygen conduit contains almost three times as much. gas as`the acetylene passage so that the quantity of acetylenev which may beaspirated from the tube I8 after the` gas-saver valves have closed isrelatively small as compared to the availableA quantity.' of oxygen.Also since the reservoir contains gas under moderately high pressure,whereaszthe stem'contains a mixture at relatively low pressure, thecapacity or quantity of gas in the reservoir may greatly exceedV that ofthe mixturein'the stem, even when the watervolume of one issubstantially equal to that of the other.

Under certain conditions, it may be desirable to employ a small pilotlight at the tip T through the use of an acetylene by-pass whichpermitsv iiow of a moderate amount of acetylene even when the gas-savervalves are closed. Under thesey circumstances, it is desirable toreverse the sequence of operations of the valves I2 and I3 so that theoxygen supply is shut off rst. If acetylene ofv medium pressure isemployed, the

aasaias principles of the present invention may be utilized byincorporating the reservoir in the rnedium pressure acetylene line,preferably in conjunction with successively-operated gas-saver valves.The reserve supply of acetylene in the reservoir thus accentuates thecontinued flow of acetylene produced by delayed action of the gassavervalve l2, to evacuate the combustible mixture in the stem S.

It is desirable that the volume of the reserve oxygen supply containedin the reservoir and the delivery conduit, be so proportioned atordinary operating pressures that the combustible mixture in the stem isevacuated after the gas-saver valves are closed, at such a velocity thatthe tendency toward backiiring is substantially eliminated. A decreasein the capacity of the reservoir increases the tendency toward backfire,While an increase in the capacity tends toward a waste of gas.

Various modiiications of the herein disclosed invention may be madeWithout departing from the scope thereof, or sacrificing any of itsadvantages.

I claim:

1. An Oxy-acetylene blowpipe comprising substantiallysimultaneously-closing valves for abruptly shutting oit the lovv ofoxygen and acetylene; a mixer; a bloWpipe tip; a stem extending fromsaid mixer for conveying combustible iixture from Said mixer to saidtip; and conduits communicating with the atmosphere only through saidtip and connecting said respective valves with said mixer, one of saidconduits having a relatively large gas capacity to maintain a pressuretherein long enough to evacuate a substantial portion of residualcombustible mixture from said stem after said valves are closed.

2. A blowpipe as claimed in claim 1, wherein said conduit of largecapacity communicates With the discharge port of the oxygen shut-01Tvalve.

3. In a blowpipe, a tubular handle; a mixer in the forward portion ofsaid handle; a blowpipe tip; acetylene and oxygen gas conduitscommunicating with the atmosphere only through said tip and extendingthrough said handle to said mixer; and substantially concurrentlyoperable valves for abruptly stopping the iiow of oxygen through saidconduits, said oxygen conduit having a portion between such oxygen valveand said mixer of relatively high gas capacity to maintain the ,gasvelocity issuing from said tip above the backward name propagation rateafter said valves have been closed, until substantially all of thecombustible mixture has passed from the blowpipe.

4. In a blowpipe, substantially instantaneously operablesimultaneously-closing shut-olf valves controlling the flow of oxygenand acetylene to said blowpipe; a mixer; a tip communicating with saidmixer; oxygen and acetylene conduits extending from said respectiveshut-off valves to said mixer, said conduits being sealed from theatmosphere except through said tip, such oxygen conduit havingsufficient gas capacity to maintain for an appreciable time a relativelyhigh gas velocity issuing from said tip after said valves have beenclosed, and until substantially all of the combustible mixture haspassed from the blowpipe.

5. A blowpipe comprising substantially concurrently-operablequick-acting shut-off valves for oxygen and acetylene respectively; amixer; a tip; a stem for delivering a gas mixture from said mixer tosaid tip; a conduit connecting one of said valves With said mixer; and asecond conduit of considerably greater capacity connecting the othervalve with said mixer, said second conduit communicating with theatmosphere only through said tip, said second conduit holding a sufcientvolume of gas at substantially line pressure to clear said stem and tipof a substantial portion of the residual combustible gas mixture thereinafter said valves'have been closed.

6. A blovvp'ipe having respective oxygen and acetylene connections; amixer; a tip; a stem for supplying a combustible gas mixture from saidmixer to said tip; substantially concurrentlyoperable quick-actingvalves for controlling the supply of oxygen and acetylene to said mixer;and oxygen and acetylene conduits connecting said respective valves Withsaid mixer, one of said conduits comprising an unventilated reservoirhaving a gas capacity in excess of that of said stem., said reservoirbeing operable when said valves are closed, to discharge the gascontained therein initially at line pressure during a suflicient periodto clear said stem of substantially all of said combustible mixture.

'1. A blovvpipe as claimed in claim 6 wherein said reservoir comprisesan enlarged zone in said oxygen conduit.

8. A blowpipe as claimed in claim 6 wherein said reservoir comprises abranch tube closed at one end and communicating at its other end withsaid oxygen conduit.

9. In a blowpipe, a fuel gas valve and a. combustion-supporting gasvalve, said valves operating abruptly and substantially concurrently; amixer; a fuel gas conduit connecting said fuel gas valve with saidmixer, and a combustionsupporting gas conduit connecting saidcombustion-supporting gas valve with said mixer; in combination with anunventilated reservoir connected With said combustion-supporting gasconduit, said reservoir having a suiiiciently large gas capacity tomaintain a relatively high gas velocity issuing from the bloWpipe tipafter said valves are closed, until substantially all of fthecombustible mixture has passed from the blowpipe.

ROBERT J. KEI-IL.

